[blackpanther-st]

OK so I have a few things in the works as I do my EV conversion for the Fiero Electro; as I work on this I am also doing a documentary on the conversion process, which I will begin posting somewhere in the near future.

The other is the article of this forum thread, which after the frustration of not seeing any verifiably reliable motor controllers in my price range and powerful enough for my conversion, I have decided to join in with the few others I have seen attempting their own motor controllers.


I have been following MpaulHolmes progress with his motor controller at Ecomodder, Paul & Sabrina's cheap 144v motor controller


http://ecomodder.com/forum/showthrea...ller-6404.html


Seeing what is happening with his project has been the most influential in my decision to do my own.


So this is what I am starting with:






Though they look like IGBT's and are made by tPowerex, they are not. IGBT's, those are actually power FET's rated at 300A each and 1000V there model # is KS621K30 New these are about $300 a piece! But I got these on Ebay for about $90 for all four. I tested each one individually at 12V and 5A and they all work as I would expect them to.


One thing I noticed in the data sheet for these FETs is that they have a natural tendency to balance current load, unlike IGBT's which have a natural tendency to become unbalanced.




For size reference, the heat sink is 8” x 12” with 1” fins and a 1/4” backing plate. The buss bars are 3/4” square aluminum.


One thing you may notice in the photo, that I am doing differently than others is that I am not connecting the B+ and M+ cables to the same point on the positive buss; instead I have one at each end, so that B+ and B- are on one end of the controller and M+ and M- are on the other. The reasons I chose to do this are one, it eliminates the possibility of the freewheeling diodes from becoming disconnected from the loop while power is still being applied to the motor in the event of a loose connection. The other reason is that it will make the connections less crowded.


Plans not yet implemented.


The positive buss will be thermally connected, but electrically isolated from the heat sink
freewheeling diodes will be thermally and electrically connected to the positive buss.
Capacitors will be in two banks on either side of the FETs and positive buss.
I plan to use copper foil with a mylar insulator to connect the capacitors to the B- and positive busses. A narrow section of copper foil will also connect M- to the freewheeling diodes.


The control section;
I have never worked with microcontrollers before, but I found the µCHAMELEON though rather pricey seemed to have what I wanted in a relatively easy format to use. And I do mean relatively, from my experience.


The µCHAMELEON came with a test application which allows you to run some basic functions from your computer over USB without having to program anything. Switching on and off each of it 18 IO pins from the application seemed to work fine as did measuring 0-5V input from the 8 pins which accept A to D input also all 18 pins were able to read IO state of connection to pin.


Now here is where I could use some help; while the programming for this seems relatively simple compared to programming I have dabbled with in the past, I have never dealt with communicating with hardware as far as microcontrollers are concerned, and I don't know how to send the strings to the device? I know that this is bacicly the first step in learning these things , but I can not find any documentation on this which is helpful to me. I am hoping that someone here can help get me started in the right direction.

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Correction !

As ga2500ev pointed out to me they are darlingtons, not FETs as I stated above; I had read the data sheet a few weeks ago and I must have gotten it mixed up with something else I was looking at. The power specks however are as I stated.

[MPaulHolmes]

Awesome! You're going bigtime! I've never used the uchamelion before. The only microcontroller programming i've done is with the ATMega8. I a little confused by the phrase "don't know how to send the strings to the device". I think you need a pwm output from a microcontroller that leads to the input of the mosfet driver, which leads to the gates of the HUGE AWESOME mosfets. You can always just use one of my ATMega8's pre-programmed. It could be like a black box. They are VERY expensive, however. We're talking like $3!

[ga2500ev]

I took a look at the data sheet for the part and it's not a power FET. It looks like it's a humongous Darlington power module. The problem is that the voltage drop is going to absolutely kill this project. The saturation voltage is 2.5V. That means that you'll lose 2.5V*300A = 750W to heat. It will severely impact your range and test your heat dissapation skills. This is about double the saturation voltage of an IGBT, which many avoid because of excessive heat.

The second problem is the turn on/turn off times are very slow, on the of 3 uS. During this transistion almost all of the power through the device is converted to heat.

It's only $90 and it seems like you have it all together. But I'm pretty sure that at some time in the future you're going to want a much more efficient power section.

ga2500ev

[Watt-a-mezz]

Hello Blackpanther & MPaul, I have been following along ,maybe learning something new. I do not think I will be building controllers, but if you develop yours(MPaul) to where you would like it to be, would I be able to purchase one? (I am one of the nervous kelly owners) Keep up the good work! Take Care, Watt

[blackpanther-st]

MpaulHolmes,
From what I understand, you can send the uchamelion individual command strings one by one, (as in being run by a host computer), or an entire program can be sent, to run on the uchamelion it self. The test application I mentioned runs on the host computer and sends individual commands, but the communication is handled from within the program. I need to learn how to do this manually. From what I have read you can use something like tellnet to do this.


My biggest disappointment with this thing is the lack of adequate documentation, including user forums.
I do know that the uchamelion has the PWM outputs I need; more than enough, I believe you can configure up to 8. I am considering using one to drive the original tachometer gage and speedometer in the fiero, without using the original ECM; my controller would essentially replace it.


I am still not sure if the uchamelion really fits what I want to do. I had thought about the Megas befor I got the uchamelion, but the learning curve looked like it would be steeper, I am not so sure now, at least there is information on the Megas. I was also taking in to consideration that I would need some sort of hardware interface to program the Mega as I understood the situation, is that correct?


I appreciate the offer for a preprogrammed one, but I really want to lay out my own functions, routines and parameters.


Moderate power testing!
In repply to ga2500ev, you are correct, They are darlingtons FETs as I stated above; I had read the data sheet a few weeks ago and I must have gotten it mixed up with something else I was looking at. The power specks however are as I stated.


I saw what you had mentioned about the saturation voltage before, and yes I was concerned about it, but most of what I have read stats IGBTs as being nearly 2V for saturation and I was already leaning towards IGBT's for the voltage head room.


So today decided to test these under a little more power, and see just how bad the saturation would be in real life. As it turns out , it is not so bad after all.


In my test I used my battery tester and bypassed the solenoid to avoid any induction spikes, ( I don't have any freewheeling diodes yet.) the tester draws about 85A when cold and drops to about 60A when it is hot; about a 10 second load test.


Two of the four darlingtons At 12v system and 1.6A of base current, (5V suppled through 2ohm power resistor) and they easily handled the 85A draw and I held the gates on until the load current droped to 60A


During the test I had a voltage meter across the C and E of the darlingtons, to measure saturation voltage. At the initial 85A, saturation voltage was just barely 2V and at 65A saturation voltage was below 1.5V and falling.


With the light weight of the Fiero I only expect to draw about 120A on flat land for normal driving at 45 MPH, so 65A on two out of the four darlingtons is realistic for average load they will see in the car. That works our to a saturation loss of under 200 Watts under average load.


Of course acceleration losses will be much higher, but I am not nearly as concerned about that as I am the average load loss; so long as It can deliver some serious Amps when I need them.


The 3 u second transition time however may be a bit more of a problem than I initially realized; I am probably going to have to clock down my PWM cycle time.

[Zemmo]

This is a very interesting controller you are coming up with. I will be following it with interest. I also thought that I would point out, that the speedometer gets its signal from the transmission. I don't know if it required an ECU to make it work, but it gets its signal from the tranny.

This is the basic amps that I draw on level ground at a constant speed in my Fiero. Every car seems to be different and even with the same equipment; a different car pulls different amps. So this is interesting info just in general and give you a frame of reference (my car runs at 120 volt and all measurements are from the battery side).

25 mph (2nd gear) is usually about 25 to 35 amps

35 mph (3rd gear) is usually about 40 to 55 amps

45 mph (3rd gear) is usually about 65 to 85 amps

55 mph (3rd gear) is usually about 100 to 110 amps

65 mph (4th gear) is usually about 125 to 135 amps

Under basic acceleration, I only pull 150 amps. Thats a nice easy acceleration. If traffic is heavy, I will pull 200 amps. After about 200 amps, it doesn't really feel like I get more acceleration even if I pull 300 amps. I think 300 amps feels about the same as 200 amps acceleration wise (once your past 25 mph). If I am accelerating onto the interstate then I am usually pulling 250 or more.

Hope this helped with your designing and planning stage.

[blackpanther-st]

Zemmo, thanks for the numbers on your fiero. That definitely is a help, seeing how it breaks down in each gear / speed range.

I must say that you are getting much better readings than I was expecting, and I will be running at 144, so my current should be even lower, if all else is the same. I think that the choice of motor has a lot to do with it, so I could be way different. Can I ask what you are running for a motor? I am going to be using a 9" GE forklift motor. Jim tells me it should be equivalent to a warp 9 for performance curves; they are built almost identically except for cosmetic changes and GE's lousy tapered shaft

[Zemmo]

I am using an Advanced DC 9" motor. Its about the same as a Warp 9, but the power ratings are rated just a little under the Warp. I don't know if those ratings are independently tested, probably not. That motor is connected to a 4 speed trans with the clutch. You can check out my website for tons of details.

I would love to go to 144 volt. All of my equipment can handle it. It is just the Fiero wouldn't like it much with the Lead Acid batteries. She is pretty heavy as it with the 20 Six Volt batteries. I am still pondering the next pack being LiFePo4 and doing the 144 Volt. Get better acceleration performance (less weight and more volts) and maybe buy more mileage. :-)

[brdriver]

old brother:
through your discribing,i advise you choose other solution,use lowe voltage and large current mould to drive.ok?
for example:Bangrong technology's product can suit your application on the driver.ok?
do you think your current mould is 1000V300A,although its price is cheap,but your machine is not feel its well point.futue you need more the kind product,it is not be provide for you.right?
other, your current mould's vol. is too large to fix easy,and its weght is effect your all run efficiency,ok?
please think its solution again!
best redards!
sober'r in shenzhen of china.

[blackpanther-st]

brdriver

300A 1000V is the ratings for each darlington transistor, there are four of them, 1200A capability, though I will be limiting at 750A - 1000A max. My system voltage will be 144V which is ideal for my motor and vehicle. the controller should be able to handle more volts providing I use capacitors that can handle it, but for my application I don't see the need for anything higher; this is already in the entry level Zilla range